Objective: Taurine has previously been suggested to protect cells against apoptosis (1, 2). The aim is to examine whether cells loaded with or depleted of taurine respond differently to the apoptosis inducing agent cisplatin. Wild type suspension Ehrlich Ascites tumor cells (EATC) were loaded with or depleted of taurine by incubating the cells in medium supplemented with 100 mM taurine or 5/100 mM b-alanine, respectively. Methods - Results: It was seen that apoptosis (caspase-3 activity) was significantly increased 3.2 ± 0.3 fold in EATC upon exposure to 10 M cisplatin (18 h). Preincubation with 100 mM taurine or 5 mM b-alanine altered the cellular taurin content in EATC from 0.024 ± 0.001 (control) to 0.687 ± 0.07 and 0.0048 ± 0.0006 mol per mg protein, respectively (HPLC technique) but neither the increase nor the decrease in taurine content had any effect on the cisplatin induced apoptosis in these cells. Caspase-3 activity was however significantly increased in EATC pre- incubated with 100 mM b-alanine prior to cisplatin exposure even though the taurine depletion was similar to the one obtained by 5 mM b-alanine preincubation. This increased caspase-3 activity in EATC cells treated with 100 mM b-alanine and cisplatin was accompanied by significant cell shrinkage (Coulter counter technique), potassium loss and sodium gain (Flame Photometry). Conclusion: We find no protective effect of taurine against cisplatin-induced apoptosis in EATC. It is speculated that the augmented cisplatin-induced apoptosis in cells exposed to high extracellular b-alanine reflects a marked b-alanine and concomitant sodium uptake which combined with a decreased Na⁺/K⁺-ATPase activity, caused by cisplatin, renders the cells incapable of regaining homeostasis, hence committing the cells to apoptosis. (1) K. Takahashi et al., Adv. Exp. Med. Biol. 583, 257 (2006). (2) U. Warskulat et al., in Methods in Enzymology, (Elsevier Inc, 2007), chap. 25, pp. 439-458.